64
Pre-tuning
The
3314A'1
Oscillator
At
this
time,
there are 2 primary concerns
which
preclude acquiring phase
lock.
.72
B.W.
~.2
(OISPLA::O
FREQ
)
where
A
;::;
1 if
the
EXT REF FREQ is <
2MHz
A = 5
if
the
EXT REF FREQ is
~
2MHZ
MODE
(cant)
Use
the
VCO
input
if you have 8 signal
that
is proportional
to
the
reference
fre-
quency. You
will
probably have
to
turn auto-acquisition
off
with
FREQ Range Hold
and
set
the
331
4A's
center
frequency manually.
Any
error between
the
VCO
in-
put
signal and
the
reference frequency
must
be corrected by
the
3314A's
PLL and
hence,
must
be
within
the
loop
bandwidth.
The
3314A's
output
frequency can
range
+
10%
to
-50%
without
losing lock.
Note
that
when
the
3314A's
output
frequency deviates >
10%
from
the
displayed frequency, one
of
the
q,
LCK lights
will
flash. This does
not
necessarily
Indicate an
out
of
lock
condition.
2. The reference
frequency
change
must
be
within
the
bandwidth
of
the
3314A
's
phase locked loop.
The
3314A's
phase-lock capability can be greatly extended if you pre-tune
its
oscillator
frequency
using
the
VCO or FM modulation capabilities.
1. The
331
4A's
output
frequency
is limited
to
+
10%
and
-50%
of
the
displayed
value.
Note
that
the
331
4A
will
not
update
its
frequency display unless the loop goes
out
of
lock
(the Fin + N
light
flashes) and Frequency Range Hold is OFF.
The approximate
bandwidth
of the phase locked loop can be determined using
this
formula:
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